1. Field of the Invention
This invention relates to devices for identifying persons by means of a portable memory medium, e.g., an IC card comprising an IC (integrated circuit), held and carried by each person to be identified, and an identification code inputted into the device by the holder of the memory medium. This invention also relates to portable memory mediums and methods of identifying persons utilized in such devices.
2. Description of the Prior Art
In recent years, devices for identifying a person utilizing a portable memory medium, i.e., a card comprising a memory medium such as a magnetic memory medium or an integrated circuit in which personal data or information is stored, are increasing in number in a variety of applications. For example, cash dispensers and automatic teller machines utilizing such identifying devices are now installed in many corners of streets in major cities.
Most commonly used method of identification adopted in such devices is that which utilizes a secret personal identification number to identify each holder of the card. The holder of the card, after inserting the card into the identifying device, inputs his secret personal identification number into the device to prove his identity.
In one type of such identifying devices, the card comprises a magnetic memory storing a secret personal identification number, which is read out by a terminal device or host computer when the card is inserted into the terminal device. The computer then compares the number inputted into the terminal device by the holder of the card with the true number read out from the card. This type of device, however, has the disadvantage that the secret personal identification number can be easily read out by a third party because the number is stored in a magnetic medium. Thus, in a certain type of a device utilizing magnetic memory cards, the secret personal identification numbers of the holders of the cards are stored in a host computer, and these numbers are compared therein with the inputted numbers. This type of a device, however, has disadvantages: the device is applicable only to on-line systems in which terminal devices are connected to a host computer by a telecommunication network; further, because a large amount of information with respect to the secret personal identification numbers must be stored and maintained at a single location, the device is inefficient and incurs high cost.
Thus, personal identification devices utilizing a card comprising an integrated circuit are attracting widening attention and are becoming increasingly popular. In this type of a device, the card usually comprises a microcomputer which has an information processing capability, and the secret personal identification number stored in the memory of the integrated circuit is compared with the inputted number by the microcomputer within the card. Thus, there is no need to output the stored identification number to an exterior device, and the security of the device is much enhanced. Further, the device is applicable to terminal devices which are not coupled to an on-line system.
However, the identification devices utilizing a card and an identification number, including those utilizing IC cards, have following disadvantages:
First, if the holder of the card forgets the personal identification number, the identification of the holder becomes impossible. Thus, users of cards tend to use one and the same identification number even when he has a plurality of cards, which reduces the security level of the whole cards.
Second, one card has only one identification number, so that if the identification number is once known to a stranger who takes possession of the card, the card can be easily abused.